Anomalous giant piezoresistance in AlAs 2D electron systems with antidot lattices

An AlAs two-dimensional electron system patterned with an antidot lattice exhibits a giant piezoresistance effect at low temperatures, with a sign opposite to the piezoresistance observed in the unpatterned region. We suggest that the origin of this anomalous giant piezoresistance is the nonuniform strain in the antidot lattice and the exclusion of electrons occupying the two conduction-band valleys from different regions of the sample. This is analogous to the well-known giant magnetoresistance effect, with valley playing the role of spin and strain the role of magnetic field.     

On the lowering of the electronic energy in model insulators due to surface reconstruction

Shubnikov-de Haas oscillations, piezoresistance, Hall mobility, and transverse “Hall” field due to mobility anisotropy have been studied on n-channel (111) Si inversion layers. The valley degeneracy was found to be 2 between 1.7 and 300 K. Under uniaxial mechanical stress the initially isotropic conductivity became strongly anisotropic. All results can be described by the existence of domains in the inversion layer.     

Giant room-temperature piezoresistance in a metal-silicon hybrid structure

Metal-semiconductor hybrids are artificially created structures presenting novel properties not exhibited by either of the component materials alone. Here we present a giant piezoresistance effect in a hybrid formed from silicon and aluminum. The maximum piezoresistive gage factor of 843, measured at room temperature, compares with a gage factor of -93 measured in the bulk homogeneous silicon. This piezoresistance boost is not due to the silicon-aluminum interface, but results from a stress induced anisotropy in the silicon conductivity that acts to switch current away from the highly conductive aluminum for uniaxial tensile strains. Its magnitude is shown, via the calculation of hybrid resistivity weighting functions, to depend only on the geometrical arrangement of the component parts of the hybrid.     

阵列式薄膜锰铜计的动态压阻响应研究

 利用直流磁控溅射薄膜工艺制备阵列式薄膜锰铜压阻计,以氧化铝作为基片和绝缘封装材料。在结构上,4个具有相同阻值的薄膜锰铜计在同一氧化铝基片上呈对称分布。51.72 GPa压力下的动态加载实验表明,4个计的压阻一致性好,无高压旁路效应,验证了薄膜锰铜压阻计动态测试的准确性和可靠性。     

Energy and momentum relaxation of charge carriers in Ge and Si under uniaxial stress

Measurements of the piezoresistance and the energy relaxation time T_?, in Ge and Si under uniaxial stress up to 4 kb are reported in the temperature range 30 K < T < 300 K. The measurements of t_? have been performed in the warm carrier range using the harmonic mixing technique. The experimental results for the piezoresistance and energy relaxation time in n-type material can roughly be understood in terms of carrier redistribution in the conduction band valleys whose degeneracy is lifted by the stress. Information is obtained from these measurements about the relative strength of ? and g type intervalley scattering in n-Si; we find nearly equal coupling strength for both scattering types. For the p-type material the experiments show convincingly that the main effect of stress on transport quantities is also caused by the lifted degeneracy of the heavy and light hole bands, as predicted already by Adams, and by Pikus and Bir. The nonlinear dependence of the piezoresistance and τ_? on the stress can very well be explained by approximating the heavy and light hole bands as spherical and parabolical and using the deformation potential constant b as a parameter. The value of ≈2eV obtained for |b| is in good agreement with earlier results for p-Ge.     

Giant piezoresistance effects in silicon nanowires and microwires

The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of depleted silicon nano- and microstructures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces independent of the applied stress. Importantly, this time-varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon.     

p型多晶硅薄膜应变因子与掺杂浓度关系理论研究

多晶硅薄膜具有良好的压阻特性,晶粒结构和掺杂浓度决定其压阻特性.一般通过调节掺杂浓度改变压阻参数,但现有的多晶硅薄膜压阻系数与掺杂浓度的理论关系和适用范围不够全面.为了完善多晶硅薄膜压阻理论,基于多晶硅纳米薄膜隧道压阻模型,以及硅价带和空穴电导质量随应力改变的机理,提出了一种p型多晶硅薄膜压阻系数算法.该算法分别求取了晶粒中性区和复合晶界区的压阻系数π_(11),π_(12)和π_(44)的理论公式,据此可以计算任意择优晶向排列多晶硅的纵向和横向压阻系数.根据材料的结构特性,求取了p型多晶硅纳米薄膜和普通多晶硅薄膜应变因子,绘制了应变因子与掺杂浓度的关系曲线,与测试结果比较,具有较好的一致性.因此,该算法全面和准确,对多晶硅薄膜的压阻特性的改进和应用具有重要意义.     

MOVPE低温生长的n型GaN电学特性研究

系统研究了采用金属有机物化学气相外延方法在740℃和900℃条件下生长的n型GaN的电学特性. 电化学电容-电压测试表明,在低温条件下采用三乙基镓作为Ga源生长有利于降低非故意掺杂n型GaN的背景杂质浓度. 另外,对重掺Si的n型GaN的霍耳效应测试表明,随着Si掺杂浓度增大,电子浓度相应线性增大,表现出杂质带导电特性,而迁移率则相应减小. 同时,原子力显微镜测试和X射线衍射测试均表明生长温度和掺杂浓度对外延材料的表面形貌和晶体质量有影响,特别是在高掺杂浓度的情况下,样品的表面形貌恶化更严重. 在所研究的 关键词： n型GaN 电子浓度 迁移率     

Studies on the coupling of interlayers in multilayered FeSi/Si amorphous films by cems

Multilayered FeSi/Si amorphous films with fixed FeSi layer thickness and different Si layer thicknesses have been studied by conversion electron Mössbauer spectroscopy at room temperature. The results showed that with decreasing the Si layer thickness, the hyperfine field of samples increased and the thickness of interface dead layers arisen from the atomic interdiffusion effect decreased. These are due to the coupling effect between the magnetic layers.     

On an estimate of the piezoresistance coefficients in diffusion layers taking account of a two-dimensional impurity distribution

The influence of finite diffusion layer width on its piezoresistance coefficient is analyzed in this paper. It is shown that a diminution in the width results in growth of the absolute value and temperature dependence of the fundamental piezoresistance coefficients.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 42–46, September, 1977.     

Role of strontium in oxide epitaxy on silicon (001)

Epitaxial oxide-Si heterostructures, which integrate the functionality of crystalline oxides with Si technology, are made possible by a submonolayer of Sr deposited on Si (001). We find by electron diffraction studies using single termination Si wafers that this Sr submonolayer replaces the top layer of Si when deposited at 650 degrees C. Supported by first-principles calculations, we propose a model for the reaction dynamics of Sr on the Si surface and its effect on oxide epitaxy. This model predicts, and we experimentally confirm, an unexplored 25 degrees C pathway to crystalline oxide epitaxy on Si.     

Studies of relativistic electron scattering at planar alignment in a thin Si crystal

Experiments on 255-MeV electron scattering under (220) planar channeling conditions in a Si crystal were carried out at the linac of the SAGA Light Source. The spatial and angular distributions of electrons penetrating through a 20-μm thick Si crystal at different incident angles with respect to the (220) plane were measured, and features characteristic of the planar alignment were identified. The experimental results were compared with computer simulations, and showed a reasonable agreement. A comparison with doughnut scattering at axial channeling in the same crystal was also performed. It was confirmed that the planar alignment effect is weaker than the axial alignment effect. These studies are important for understanding the basic mechanism of electron scattering and radiation processes in a crystal.     

双栅调控的硅量子线中的库仑振荡效应

基于单电子隧穿和库仑阻塞效应,研究了硅量子线中的单电子输运特性.利用绝缘体上硅薄膜材料作为衬底构建侧栅结构的硅量子线单电子晶体管,通过背栅和侧栅对量子线的电子输运特性进行调制.实验发现,在硅量子线中分别观察到背栅和侧栅调制的单电子效应和库仑振荡现象.从微分电导的二维灰度轮廓图,清楚地观察到了库仑阻塞区,说明由于栅压导致在硅量子线中形成了库仑岛. 关键词： 库仑振荡 单电子效应 硅量子线     

压阻式新型矢量水听器设计

本文介绍了矢量水听器的应用，分析了压阻式矢量水听器的基本工作原理。提出了采用压阻原理进行矢量水听器设计的方案思想，并从结构灵敏度、输出特性、谐振频率几方面进行了设计分析，展望了将MEMS技术应用于矢量水听器的远景优势。     

Surface morphology of the Si(310) substrate used for molecular beam epitaxy of CdHgTe: I. Clean Si(310) surface

The effect of vacuum annealing on the morphology of hydrogenated and oxidized Si(310) surfaces is investigated by scanning tunnel microscopy, reflection high-energy electron diffraction, and low-energy electron diffraction. It is found that after desorption of a passivating coating, the surface has a strongly developed profile formed preferentially by steps two monolayers in height. Annealing at a temperature of 900±15°C with subsequent abrupt cooling leads to faceting of the surface by (510) planes. The presence of steps two monolayers in height on the Si(310) surface allows one to use Si crystals oriented along the (310) plane as the substrate for heteroepitaxy of the II–VI compounds.     

Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.     

Pressure-induced colossal piezoresistance effect and the collapse of the polaronic state in the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn2O7

We have investigated the effect of hydrostatic pressure as a function of temperature on the resistivity of a single crystal of the bilayer manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7). Whereas a strong insulating behaviour is observed at all temperatures at ambient pressure, a clear transition into a metallic-like behaviour is induced when the sample is subjected to a pressure (P) of ~1.0 GPa at T < 70 K. A huge negative piezoresistance ~10(6) in the low temperature region at moderate pressures is observed. When the pressure is increased further (5.5 GPa), the high temperature polaronic state disappears and a metallic behaviour is observed. The insulator to metal transition temperature exponentially increases with pressure and the distinct peak in the resistivity that is observed at 1.0 GPa almost vanishes for P > 7.0 GPa. A modification in the orbital occupation of the e(g) electron between 3d(x(2)-y(2)) and 3d(z(2)-r(2)) states, as proposed earlier, leading to a ferromagnetic double-exchange phenomenon, can qualitatively account for our data.     

负偏压热灯丝CVD金刚石膜核化和早期生长的研究

利用扫描电子显微镜、Raman谱和X射线光电子能谱，研究了Si衬底上热灯丝CVD金刚石膜的核化和早期生长.在-300V和100mA条件下预处理15min，镜面抛光的Si(100)表面上金刚石核密度超过了10⁹cm^-2，但是核的分布极不均匀且可分为三个区域：A区，边缘处以锥体为主；B区，位于边和中心之间过渡区是纳米金刚石；C区，中心处有SiC层.无偏压下生长4h后，A区形成许多大而弧立的金刚石颗粒，B区成为织构金刚石膜，而C区变为含有大量缺陷的连续金刚石膜.衬底负 关键词：     

XPS investigation of electron beam effects on a trimethylsilane dosed Si(100) surface

A trimethylsilane covered Si(100) surface at temperature −120°C was bombarded by 1.3 keV electrons for various time intervals. The core level Si2p and C1s electrons were studied after each electron bombardment by use of X-ray photoelectron spectroscopy. The spontaneous dissociation of TMSiH on the Si(100) surface was observed judging from the formation of C---C bonds. The C---C and C---Si bonds increased initially and then saturated after 20 min of electron exposure. The binding energy of C1s in C---C and C---Si bonds and that of Si2p in Si---C bonds showed an opposite behavior under electron irradiation. The former increased and the latter decreased at the beginning of the irradiation and then both increase rate and decrease rate reduced. From the previous results of electron stimulated desorption and temperature programmed desorption, and the variation of electron density distribution around C and Si, it is concluded that the de-hydrogenation in C---H_n and Si---C---H_m bonds was induced and new Si---C and C---Si bonds were formed by electron irradiation on TMSiH covered Si(100) surface.